Forbes estimates Zuckerberg was worth $4 billion in 2010 and is worth $13.5 billion today. Also, according to Forbes, the 2011 Billionaires List breaks two records: total number of listees (1,210) and combined wealth ($4.5 trillion). Read the full story here, and you can read a bio of all 1,210 people on the 2011 Billionaires List here.